Electrochromic (EC) devices are typically multi-layer stacks including (a) at least one layer of electrochromic material that changes its optical properties in response to the application of an electrical potential, (b) an ion conductor (IC) layer that allows ions, such as lithium ions, to move through it, into and out from the electrochromic material to cause the optical property to change, while preventing electrical shorting, and (c) transparent conductor layers, such as transparent conducting oxides (TCOs), over which an electrical potential is applied to the electrochromic layer. In some cases, the electric potential is applied from opposing edges of an electrochromic device and across the viewable area of the device. The transparent conductor layers are designed to have relatively high electronic conductance properties. Electrochromic devices may have more than the above-described layers such as ion storage or counter electrode layers that optionally change optical states.
Due to the physics of the device operation, proper functioning of the electrochromic device depends upon many factors such as ion movement through the material layers, the electrical potential required to move the ions, the sheet resistance of the transparent conductor layers, and other factors. Size and shape of the electrochromic device play an important role in the uniformity of coloration across the face of the device. Additionally, the size and shape of the device play a role in the transition of the device from a starting optical state to an ending optical state (e.g., from colored to bleached state or bleached to colored state). The conditions applied to drive the transitions and hold an optical end state can have quite different requirements for different shaped devices.
Further, where an electrochromic device is of a non-rectangular shape, certain fabrication processes are more difficult. For example, laser edge delete (LED) and bus bar pad expose (BPE) operations utilize square/rectangular laser patterns which are oriented parallel or perpendicular to the local edge of the substrate. These patterns are defined by vector files that are implemented by the scanner/laser. While these patterns lend themselves to simple processing with rectangular-shaped devices, they are much more difficult to implement on shapes that are more complex, for example shapes having curved edges or edges that are at non-right angles to adjacent edges.